Vijayadasami (Sanskrit: विजयदशमी), also known as Dussehra (Sanskrit: दशहरा), is a major Hindu festival celebrated at the end of Navratri every year. It is observed on the full moon day in the Hindu calendar month of Ashvin, which typically falls in the Gregorian months of September and October.

Vijayadasami is observed for different reasons and celebrated differently in various parts of the Indian subcontinent. In the eastern and northeastern states of India, Vijayadashami marks the end of Durga Puja, remembering goddess Durga's victory over the buffalo demon to help restore Dharma. In the northern, southern and western states, the festival is synonymously called Dussehra (also spelled Dasara, Dashahara). In these regions, it marks the end of "Ramlila" and remembers god Rama's victory over the demon Ravana, or alternatively, it marks a reverence for one of the aspects of goddess Devi such as Durga or Saraswati
Dussehra in 2017 is on Saturday, the 30th of September (30/9/2017).
Source: https://en.wikipedia.org